The technology of the present disclosure relates to an optical scanner for use in, e.g., an image forming device such as a copier, a printer or the like and an image forming device provided with the optical scanner.
In general, an optical scanner includes a housing, a polygon mirror, an imaging lens and a cover member mounted to the housing. The polygon mirror and the imaging lens are accommodated within the housing.
In this optical scanner, the light of a light source is reflected by the polygon mirror and is incident on a photosensitive drum of an image forming device through the imaging lens. Since the polygon mirror is rotationally driven, the reflected light of the polygon mirror passed through the imaging lens scans the surface of the photosensitive drum. Thus, an electrostatic latent image is formed on the surface of the rotating photosensitive drum.
If dust entering the housing of the optical scanner adheres to a reflection surface of the polygon mirror, there is posed a problem in that an image becomes poor due to a reduced light quantity or other causes.
As a solution to this problem, there is known an optical scanner in which an urethane foam is compressed and inserted into a clearance between the imaging lens and the cover member. With this configuration, the polygon mirror is sealed by the housing, the cover member, the urethane foam and the imaging lens. This restrains dust from adhering to the polygon mirror.
The temperature of a lens tends to increase during the use of the optical scanner. If the lens temperature increases to a great extent, the optical properties of the lens undergo a change. This poses a problem in that an optical scanning accuracy decreases and an image becomes poor.
The aforementioned optical scanner has a structure in which the urethane foam and the cover member overlap in two layers on the imaging lens. For that reason, it is difficult to efficiently dissipate heat from the imaging lens through the urethane foam and the cover member. Since the urethane foam itself has a heat insulating property, it become more difficult to reduce the temperature of the imaging lens.